/*
 * This file is part of Awake FILE. 
 * Awake FILE: Easy file upload & download over HTTP with Java.                                    
 * Copyright (C) 2015,  KawanSoft SAS
 * (http://www.kawansoft.com). All rights reserved.                                
 *                                                                               
 * Awake FILE is free software; you can redistribute it and/or                 
 * modify it under the terms of the GNU Lesser General Public                    
 * License as published by the Free Software Foundation; either                  
 * version 2.1 of the License, or (at your option) any later version.            
 *                                                                               
 * Awake FILE is distributed in the hope that it will be useful,               
 * but WITHOUT ANY WARRANTY; without even the implied warranty of                
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU             
 * Lesser General Public License for more details.                               
 *                                                                               
 * You should have received a copy of the GNU Lesser General Public              
 * License along with this library; if not, write to the Free Software           
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  
 * 02110-1301  USA
 *
 * Any modifications to this file must keep this entire header
 * intact.
 */
/*
 * @(#)Base64.java	1.3 01/12/03
 *
 * Copyright 2002 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package org.kawanfw.commons.util;

import java.util.prefs.Preferences;

/**
 * Static methods for translating Base64 encoded strings to byte arrays and
 * vice-versa.
 * 
 * @author Josh Bloch
 * @version 1.3, 12/03/01
 * @see Preferences
 * @since 1.4
 */
public class Base64 {
    /**
     * Translates the specified byte array into a Base64 string as per
     * Preferences.put(byte[]).
     */
    public static String byteArrayToBase64(byte[] a) {
	return byteArrayToBase64(a, false);
    }

    /**
     * Translates the specified byte array into an "aternate representation"
     * Base64 string. This non-standard variant uses an alphabet that does not
     * contain the uppercase alphabetic characters, which makes it suitable for
     * use in situations where case-folding occurs.
     */
    static String byteArrayToAltBase64(byte[] a) {
	return byteArrayToBase64(a, true);
    }

    private static String byteArrayToBase64(byte[] a, boolean alternate) {
	int aLen = a.length;
	int numFullGroups = aLen / 3;
	int numBytesInPartialGroup = aLen - 3 * numFullGroups;
	int resultLen = 4 * ((aLen + 2) / 3);
	StringBuffer result = new StringBuffer(resultLen);
	char[] intToAlpha = (alternate ? intToAltBase64 : intToBase64);

	// Translate all full groups from byte array elements to Base64
	int inCursor = 0;
	for (int i = 0; i < numFullGroups; i++) {
	    int byte0 = a[inCursor++] & 0xff;
	    int byte1 = a[inCursor++] & 0xff;
	    int byte2 = a[inCursor++] & 0xff;
	    result.append(intToAlpha[byte0 >> 2]);
	    result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
	    result.append(intToAlpha[(byte1 << 2) & 0x3f | (byte2 >> 6)]);
	    result.append(intToAlpha[byte2 & 0x3f]);
	}

	// Translate partial group if present
	if (numBytesInPartialGroup != 0) {
	    int byte0 = a[inCursor++] & 0xff;
	    result.append(intToAlpha[byte0 >> 2]);
	    if (numBytesInPartialGroup == 1) {
		result.append(intToAlpha[(byte0 << 4) & 0x3f]);
		result.append("==");
	    } else {
		// assert numBytesInPartialGroup == 2;
		int byte1 = a[inCursor++] & 0xff;
		result.append(intToAlpha[(byte0 << 4) & 0x3f | (byte1 >> 4)]);
		result.append(intToAlpha[(byte1 << 2) & 0x3f]);
		result.append('=');
	    }
	}
	// assert inCursor == a.length;
	// assert result.length() == resultLen;
	return result.toString();
    }

    /**
     * This array is a lookup table that translates 6-bit positive integer index
     * values into their "Base64 Alphabet" equivalents as specified in Table 1
     * of RFC 2045.
     */
    private static final char intToBase64[] = { 'A', 'B', 'C', 'D', 'E', 'F',
	    'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S',
	    'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',
	    'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's',
	    't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5',
	    '6', '7', '8', '9', '+', '/' };

    /**
     * This array is a lookup table that translates 6-bit positive integer index
     * values into their "Alternate Base64 Alphabet" equivalents. This is NOT
     * the real Base64 Alphabet as per in Table 1 of RFC 2045. This alternate
     * alphabet does not use the capital letters. It is designed for use in
     * environments where "case folding" occurs.
     */
    private static final char intToAltBase64[] = { '!', '"', '#', '$', '%',
	    '&', '\'', '(', ')', ',', '-', '.', ':', ';', '<', '>', '@', '[',
	    ']', '^', '`', '_', '{', '|', '}', '~', 'a', 'b', 'c', 'd', 'e',
	    'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r',
	    's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4',
	    '5', '6', '7', '8', '9', '+', '?' };

    /**
     * Translates the specified Base64 string (as per Preferences.get(byte[]))
     * into a byte array.
     * 
     * @throws IllegalArgumentException if <tt>s</tt> is not a valid Base64
     *        string.
     */
    public static byte[] base64ToByteArray(String s) {
	return base64ToByteArray(s, false);
    }

    /**
     * Translates the specified "aternate representation" Base64 string into a
     * byte array.
     * 
     * @throw IllegalArgumentException or ArrayOutOfBoundsException if
     *        <tt>s</tt> is not a valid alternate representation Base64 string.
     */
    static byte[] altBase64ToByteArray(String s) {
	return base64ToByteArray(s, true);
    }

    private static byte[] base64ToByteArray(String s, boolean alternate) {
	byte[] alphaToInt = (alternate ? altBase64ToInt : base64ToInt);
	int sLen = s.length();
	int numGroups = sLen / 4;
	if (4 * numGroups != sLen)
	    throw new IllegalArgumentException(
		    "String length must be a multiple of four.");
	int missingBytesInLastGroup = 0;
	int numFullGroups = numGroups;
	if (sLen != 0) {
	    if (s.charAt(sLen - 1) == '=') {
		missingBytesInLastGroup++;
		numFullGroups--;
	    }
	    if (s.charAt(sLen - 2) == '=')
		missingBytesInLastGroup++;
	}
	byte[] result = new byte[3 * numGroups - missingBytesInLastGroup];

	// Translate all full groups from base64 to byte array elements
	int inCursor = 0, outCursor = 0;
	for (int i = 0; i < numFullGroups; i++) {
	    int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
	    int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
	    int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
	    int ch3 = base64toInt(s.charAt(inCursor++), alphaToInt);
	    result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));
	    result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
	    result[outCursor++] = (byte) ((ch2 << 6) | ch3);
	}

	// Translate partial group, if present
	if (missingBytesInLastGroup != 0) {
	    int ch0 = base64toInt(s.charAt(inCursor++), alphaToInt);
	    int ch1 = base64toInt(s.charAt(inCursor++), alphaToInt);
	    result[outCursor++] = (byte) ((ch0 << 2) | (ch1 >> 4));

	    if (missingBytesInLastGroup == 1) {
		int ch2 = base64toInt(s.charAt(inCursor++), alphaToInt);
		result[outCursor++] = (byte) ((ch1 << 4) | (ch2 >> 2));
	    }
	}
	// assert inCursor == s.length()-missingBytesInLastGroup;
	// assert outCursor == result.length;
	return result;
    }

    /**
     * Translates the specified character, which is assumed to be in the
     * "Base 64 Alphabet" into its equivalent 6-bit positive integer.
     * 
     * @throw IllegalArgumentException or ArrayOutOfBoundsException if c is not
     *        in the Base64 Alphabet.
     */
    private static int base64toInt(char c, byte[] alphaToInt) {
	int result = alphaToInt[c];
	if (result < 0)
	    throw new IllegalArgumentException("Illegal character " + c);
	return result;
    }

    /**
     * This array is a lookup table that translates unicode characters drawn
     * from the "Base64 Alphabet" (as specified in Table 1 of RFC 2045) into
     * their 6-bit positive integer equivalents. Characters that are not in the
     * Base64 alphabet but fall within the bounds of the array are translated to
     * -1.
     */
    private static final byte base64ToInt[] = { -1, -1, -1, -1, -1, -1, -1, -1,
	    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	    -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1,
	    -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
	    13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1,
	    -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
	    41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 };

    /**
     * This array is the analogue of base64ToInt, but for the nonstandard
     * variant that avoids the use of uppercase alphabetic characters.
     */
    private static final byte altBase64ToInt[] = { -1, -1, -1, -1, -1, -1, -1,
	    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	    -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, -1,
	    62, 9, 10, 11, -1, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 12, 13,
	    14, -1, 15, 63, 16, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
	    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 17, -1, 18,
	    19, 21, 20, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39,
	    40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 22, 23, 24, 25 };

    /*
     * public static void main(String args[]) { int numRuns =
     * Integer.parseInt(args[0]); int numBytes = Integer.parseInt(args[1]);
     * java.util.Random rnd = new java.util.Random(); for (int i=0; i<numRuns;
     * i++) { for (int j=0; j<numBytes; j++) { byte[] arr = new byte[j]; for
     * (int k=0; k<j; k++) arr[k] = (byte)rnd.nextInt();
     * 
     * String s = byteArrayToBase64(arr); byte [] b = base64ToByteArray(s); if
     * (!java.util.Arrays.equals(arr, b))
     * //System.out.println("Dismal failure!");
     * 
     * s = byteArrayToAltBase64(arr); b = altBase64ToByteArray(s); if
     * (!java.util.Arrays.equals(arr, b))
     * ///System.out.println("Alternate dismal failure!"); } } }
     */
}
